The goal of this proposal is to develop a general understanding at the molecular level of gene expression during avian erythroid development. Avian erythropoiesis will be studied as a model developmental system, and the differences in developmental regulation between embryonic and adult chicken erythropoiesis will be of special interest. This work will focus on regulation at the nucleic acid level: gene organization and structure-function relationships, chromatin structure, transcription, and RNA transport and processing. The immediate approach taken will be largely biochemical, i.e. the isolation, characterization and structural analysis of the component DNA and RNA species involved. These results will lead to future applications in the areas of in vitro transcription and DNA transformation studies. The chicken globin gene family will be a major focal point for these studies. A "library of recombinant bacteriophage containing the entire chicken genome has been prepared. Most, if not all, of the chicken globin genes have been isolated, both those expressed in the early embryo and in the adult. Studies on the organization and structure of these genes will continue using standard molecular biological techniques (Southern blotting, restriction enzyme mapping, electron microscopic visualization, and DNA sequencing). Globin RNA transcription and processing will be examined by the isolation of nuclear RNA from erythroid cells (adult and embryonic) and the use of specific recombinant DNA hybridization probes to detail the structure and metabolic fate of globin precursor RNAs. The expression of the other less prevalent mRNAs of erythroid cells will also be studied. The red cell-specific histone H5 gene (along with the other chicken histone genes) will be isolated from the recombinant library as will red cell membrane protein genes such as those coding for spectrin and actin. In this way, we can derive a more global picture of developmental regulation as it occurs during avian erythropoiesis.